I have trouble working with the HT compass sensor. I already use Xander's calibration code to calibrate it. But still it gives biased readings. Then I write a few testing programs and find that: in the relative mode, the negative 180 degrees (0~-180) covers more than a half circle than the positive degrees, i.e. some degrees are distributed more intensively. Does anyone have ideas about the possible causes?

There are some ordinary devices in the room, like laptops and mobile phones. I tried not to place my robot next to them. Do they make great disturbance? Sometimes the reading varies up to 10 degrees if I displace it for only 10 cm or so.

Actually I use a different design from the standard TriBot mentioned in your code. But I follow the two requirements: the robot should rotate no faster than 360 degree/20s and totally have rotated more than 360 degrees. I don't quite understand its principles of calibration.

Well, I don't know how it works exactly with the HT one, but with the Dexter Industries one, my driver does all the calibration work. What it does, it tries to get the minimum and maximum field values as it rotates and get an average. This allows it to calculate the amount of magnetic field disturbance. The calibration value is subtracted from the magnetic field strengths before the heading is calculated. I can only assume the HT sensor does something similar.I would suggest turning the robot about 540 degrees, or so.

yike... the hitechnic compass does not seem to do tilt compensation!? I assumed it did as a compass will not be much useful without tilt compensation. It looks like one will have to get an accel sensor to work with this hitechnic compass to make it really any close to be reliable for a robot to use.

Well, $50 for the tilt compensated compass is not bad at all... considering it will cost me over $30 to implement a more generic solution (my center's development head proved it works): - LSM303DLHC 3D Compass and Accelerometer Carrier, http://www.pololu.com/catalog/product/2124... - a very nice small Breadboard connector from mindsensors: http://www.mindsensors.com/index.php?mo ... AGE_id=148- or strip one end of the cable hooking onto a tiny breadboard I want to get cheap on the cost.

No, the HT compass has no 3D accelerometer inside. So you need to make sure it's mounted horizontally, as indicated on the product page

Quote:

The HiTechnic compass sensor will only operate correctly in a horizontal plane so you must keep the compass level for it to read correctly. This is very important so remember this when you build it into your robot.

You also cannot access the raw field data, as far as I am aware of, so combining a HT compass with an accelerometer, will not help you compensate, you'll need all 3 field strengths.

If you have the math to make it work with the Mindsensors one, I'll be happy to include it in my Suite and make it available to everyone.

The HiTechnic compass sensor will only operate correctly in a horizontal plane so you must keep the compass level for it to read correctly. This is very important so remember this when you build it into your robot.

Yea... it is my fault. I just assumed it did without reading it carefully. Well, bummer. :-[

mightor wrote:

If you have the math to make it work with the Mindsensors one, I'll be happy to include it in my Suite and make it available to everyone.= Xander

According to the developer at Mindsensors, the tilt compensation is also built-in. Well, I'll test it when i get one.

Who is online

Users browsing this forum: No registered users and 1 guest

You cannot post new topics in this forumYou cannot reply to topics in this forumYou cannot edit your posts in this forumYou cannot delete your posts in this forumYou cannot post attachments in this forum